Rapid in-motion heading alignment using time-differenced carrier phases from a single GNSS antenna and a low-grade IMU

Despite advancements in global navigation satellite system/inertial navigation system (GNSS/INS) integrated systems, the challenge of achieving rapid and accurate initial heading alignment remains, particularly in low-grade IMUs and marine applications with swaying conditions. This study introduces an innovative in-motion heading alignment method utilizing time-differenced carrier phases (TDCP) from a single GNSS antenna and a low-grade IMU based on the fundamental principle of trajectory similarity. The heading angle is determined by comparing the dead reckoning (DR)-derived trajectory with the TDCP-derived trajectory. This is achieved using gyro measurements and the delta position from TDCP solutions. The proposed alignment method can be implemented in real-time and the alignment period is just 1 s, which indicates that the method could continuously output heading when the carrier is in motion. We not only validate the effectiveness of the proposed alignment method in land vehicle applications, but also in maritime vessels, like unmanned surface vessels (USV), and unmanned underwater vehicles (UUV). In addition, we evaluated the impact of challenging ocean conditions and mounting angle errors on the proposed alignment method. Experimental results show that the heading could be determined with an accuracy of 0.49 degrees, 3.10 degrees, and 2.31 degrees at a 95% confidence level for the land vehicle, USV, and UUV tests, respectively. Besides, the RMS of the alignment errors calculated by our method reaches 0.24 degrees, 1.42 degrees, and 1.19 degrees for the land vehicle, USV, and UUV tests, respectively.